Line drop compensator



Oct. 22, 1940. w, J, M H 2,218,762

LINE DROP COMPENSATOR Filed Jan. 20, 1938 Fig. I.

I 7 IR For 1 E For .3 E +30'LEA0 12:5

v- 86 Fig. 3. 1x=.5 1R =.'aee For 3 A -30LA6 I E u=.aee .30

I IR= -.J

POTENTIAL CIRCUIT CURE EN? CIRCUIT TO REGULAT'INO RELAY CIRCUIT POTENTIAL TRANSFORMER CURRENT TRANSFORMER Inventob: Willaffd J. Flc Lachlan,

by flan/Z6. is Attornez.

Patented Oct. 22, 1940 UNITED STATES mm na'or COMPENSATOR Willard J. McLachlan, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application January 20, 1939, Serial No. 251,992

9 Claims.

This invention relates .to line drop compensators and more particularly to improvements in the line drop compensator described and claimed in an application Serial No. 102,221, (now Patent 2,147,490 granted February 14, 1939) flied September 23, 1936, in the name of William W. Kuyper and assigned to the assignee of the present application.

In the Kuyper compensator two voltages, each 10 having two components, are inserted in a potential circuit. These components are derived separately from two resistance and two reactance voltage dropsin a current circuit. The potential circuit is energized by the potential of a main 15 alternating current line and the current circuit is energized by the current in the main line. For an angle between the current and potential of the main line at unity power factor the component derived from one resistance voltage drop a is made equal to cos 0 times the desired resistance compensation voltage and the component derived irom'one reactance voltage drop is made equal to sin 0 times the desired resistance compensation voltage. These two components joint- 35 ly produce the desired resistance compensation voltage. Likewise, the component derived from the remaining reactance voltage drop is made equal to cos 0 times the desired reactance compensation voltage and the component derived from the remaining resistance voltage drop is made equal to sin 0 times the desired reactance compensation voltage. These two components jointly produce the desired reactance compensation voltage. Adjustment of the resistance compensation voltage requires the adjustment of both its components and similarly adjustment of the reactance compensation voltage requires the adjustment of both its components.

This invention is characterized by producing the two voltage drop components of the resistance compensation by one adjustable current and by producing the two voltage drop components of the reactance compensation with another adjustable current. In this manner the resistance compensation is adjusted by varying only one element and the reactance compensation is adjusted by varying only one element.

An object of the invention is to provide a new and improved line drop compensator.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Figs. 1, 2 and 3 are vector is diagrams for illustrating the principle of operation of the invention, Fig. 4 is a circuit diagram of an embodiment of the invention, and Fig. 5 illustrates a modification.

Referring now to the drawing, and more particularly to Figs. 1, ,2 and 3. Fig. 1 illustrates the 6 in-phase relationship (0=0), such as occurs at, unity power factor on a single phase circuit. In this diagram, E is the potential of the potential circuit, I is the current of the current circuit, Ir is the desired resistance compensation voltage, 10 and 1:1: is .the desired reactance compensation voltage. In other words, Ir is the voltage produced by the current I flowing through a resistance 1' because cos 0=1 and sin 0=0, and I1: is the voltage drop caused by the current I flowing 18 through a reactance :1: because cos 0=1 and sin 0=0. In Fig. 2 the current I is shown leading the potential E by thirty degrees (0=+30). This is a typical unity power factor phase displacement between line-to-line voltage and line curg0 rent in three phase circuits. 11:.866 (cos 30) and I:c=.5 (sin 30) are the resistance and reactance voltage 'drops caused by the current I flowing through a resistance of .8661' and a reactance or .5r. The vector sum of these voltages will then be the same as Ir in Fig. 1, so that when the thirty-degree leading current flows through a resistance of .8661' and a reactance of .5r (in the negative direction), the resultant line drop compensation voltage remains unchanged, that is to say, it is the same as in Fig. 1. In a like manner, for the reactance compensation the vector Ia:=.866 and the vector 1r=-.5 are the voltage drops produced by the current'I flowing through a reactor having a value of .8662: and a resistor having the value of .51. These two vectors combine to form a resultant vector which corresponds. in magnitude and phase to the reactance compensation shown in Fig. 1. In Fig. 3 the vector relations are shown when true line 40 drop compensation is produced by a current which lags by thirty degrees (6=30). In this case, in order to get proper line drop compensation the'signs oi theone-half valued vectors have to be reversed. v

Referring now to Fig. 4, the potential circuit i has connected therein a pair of reactance elements 2 and 3 and a pair of resistance elements 4 and 5. The reactance elements may be ordinary reactors or they may be reactance transformers. *rn latter form is illustrated. Such transformers usually have a core provided with an air gap so as to draw a relatively large magnetizing current. Reactor 2 is provided with a .866 valued tap 6 and the resistor 4 is provided 5 value of one-half the full value of resistor 4. The

current circuit 8 has connected therein a pair of current transformers 9 and I0. These are provided with tapped secondaries or other equivalent means for adjusting their ratios so as to adjust their current outputs. Adjustment of transformer 9 produces the resistance compensation adjustment, and adjustment of the transformer Ill produces the reactance compensation adjustment. Connections are made between the transformers 9 and I and the resistance and reactance elements by means of a plurality of switches. These switches comprise a pair of reversing switches and I2, a pair of single-pole doublethrow switches l3 and I4 and a pair of singlepole single-throw switches II and ll.

The operation is as follows. ;When it is desired to operate the compensator with a single phase main circuit in which the potential in the potential circuit and the current in the current circult 2 are in phase, the switch i3 is closed in its right-hand position and switch I4 is closed in its left-hand position so as to connect to the full valued taps of the reactor 2 and the resistor 4 respectively. Switches l5 and l6 are closed and switches II and I2 may be in any position. The result is that current from the current transformer 9 flows through the full value of the resistor 4 by way of switches i4 and I6, while current from the current transformer I0 flows through the full value of the reactor 2 by way of switches l3 and II.

If now it is desired to use the compensator to give true line drop compensation when the current in the current circuit leads or lags the potential in the potential circuit by thirty de- .grees, the switches l2 and H are closed in their left-hand and right-hand positions respectively so as to make connection to the .866 valued taps on the reactor 2 and the resistor 4, switches II and II are opened and switches and I2 are closed in their right-hand or left-hand positions depending upon whether the current leads or legs the potential, respectively. For example, when the switches H and I2 are closed in their right-hand positions the current from the current transformer 9 will flow through the .866

I part of the resistor 4, then through the switch M, then through the half valued reactor 2 by way,

of the switch l2. It will be noted that the current flows through the reactor 2 in the opposite direction with respect to the way it flows through the resistor 4, so that the voltage drops produced by the current output of the transformer 9 flowing. through theresistor 4' and reactor 2 will be .86611' and -.5Ix which, as

shown in Fig. 2, will result in the correct amount of resistance compensation for a thirty-degree leading current. Similarly, the current from the current transformer ill will flow through the resistor 5 in the normal direction, thereby producing a voltage drop of +.5Ir and will then flow through the reactor 2 by means of the .866

valued tap, thus producing a voltage drop of +.866I:r. As will be seen from Fig. 2, the combination of these two vectors gives the correct amount of reactance drop compensation for a thirty-degree leading current.

duce correct line drop compensation for a thirty-' degree lagging current.

In Fig. 5 the arrangement is somewhat simplifled by using but a single resistor I1 and a single reactor l8, each having the same ohmic value. The resistor has two pairs of terminals between which the resistance is in the ratio of 1:.577 and similarly the reactor has two pairs of terminals between which the reactance is in the ratio of 1:577. The current circuit contains a pair of special current transformers II and 20 provided ,with taps on their primary windings for adjusting their transformation ratios and thus, in eifect, adjusting their output currents. In addition, their secondary windings are provided with adjustable tap connections for varying the current outputs in the ratio of 11.866. A transfer switch 2| is provided for changing the connections between 'those required for single phase operation and those.

required for three phase operation and a pair of reversing switches 22 and 23 are provided for reversing the polarity or phase of the voltage drops in the .577 valued resistance and reactance. Theoperation is as follows. For single phase operation switches 22 and 23 are left open and switch 2| is closed in its left-hand position. rmthese connections the output current of the transformer l8 flows through the unity valued portion of the resistor l1 and the output current of the transformer 20 flows through the unity valued portion of the reactor 1:, thereby tions depending upon whether the line current leads or lags the potential by thirty degrees. Thus, the .866 valued current flowing through the unity valued portions of the resistor l1 and are closed in, their right-hand or left-hand poeithe reactor l8 produces the positive .868 valued resistance and reactance drops in the potential circuit, while the .866 valued current flowing through the .577 valued portions of the resistor l1 and the reactor I. in opposite directions produces the positive and negative .5 valued resistance and reactance voltage drops.

While there have been shown and described particular embodiments of this invention, it will be'obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appendedclaims to cover all such changes andmodiflcations as fall within the true spirit and scope of the invention.

What I claim as new and desire to Letters Patent of the United States, is:

1. In a line drop compensator, a potential circuit, resistance and reactance connected therein, a current circuit carrying a current making an angle 0 with the potential of said potential circuit, means for deriving from the current in said current circuit a pair of separately adjustable magnitude currents so as to adJust the resistance and reactance settings of said compensator, connections between one of said means and said resistance and reactance for producing a voltage drop in part of said resistance which is equal to cos times a predetermined resistance voltage drop and so as to produce a voltage drop in part of said .reactance which is equal to sin 0 times said predetermined resistance voltage drop, and connections between the other of said means and said reactance and resistance for producing a voltage drop in another part of said reactance which is equal to cos 0 times a predetermined reactancevoltage drop and for producing a voltage drop in another part of said resistance which is equal to sin 6 times said predetermined reactance voltage drop.

. 2; In a line drop compensator, a potential circuit,resistance and reactance connected therein, a current circuit, first and second current transformers connected therein, means for adjusting the ratios of said current transformers so as to adjust the resistance and reactance settings of said compensator, connections between said first current transformer and parts of said resistance and reactance for producing a voltage drop in said resistance which is proportional to .866 times a predetermined resistance voltage drop and'so as to produce a voltage drop in said reactance which is proportional to .5 times said predetermined resistance voltage drop; and connections between said second current transformer and other parts of said reactance and resistance .for producing a voltage drop in said reactancelwhich is proportional to .866 times said predetermined reactance voltage drop and-for producing a voltage drop in said resistance which is-proportional to .5 times said predetermined reactance voltage drop.

3. In a line drop compensator, .a potential circuit, equal amountsof resistance and reactance connected therein, a current circuit, first and second variable ratio current transformers connected therein for adjusting respectively the resistance and reactance settings of said compensator, and switching means for connecting the secondary windings of said current-transformers to. said resistance and reactance, said switching means having a first position for causing the current output of the first current transformer to produce a voltage drop in said resistancewhich isv proportional to a predetermined value and -causing the current output of the second current transformer to produce a voltage drop in said reactance which is proportional to a predetermined value, said switching means having a second position for causing the current output of said first current transformer to produce voltage drops in said resistance and reactance which are proportional respectively to plus .866 and plus .5 times the voltage drops produced therein when said switching means is in its first position and for causing the current output of said second current transformer to produce voltage drops in said reactance and resistance which are proportional respectively to plus .866 and minus .5 times the voltage drops produced therein when said switching means is in its first position, said switching means having a third position for causing the current output of said first current transformer to produce voltage drops in said resistance and reactance which are proportional respectively to plus the voltage drops produced .866 and minus .5 times therein when said transformer to vflow through said switching means is in its first position and for causing the current output of said second current transformer to produce voltage drops in said reactance and resistance proportional respectively to plus .866 and plus .5 times the voltage drops produced therein when said switching means is in its first position 4. In a line drop compensator, a potential circuit, a pair of resistors and-a pair of reactors serially connected therein, the relative values of said resistors being in the ratio of .866:.5, the relative values of said reactors being in the ratio of .866:.5, a current circuit, first and second current transformers connected therein, connections for causing the current output of the first current transformer to flow through said .866 valued resistor and said .5 valued reactor in the same relative directions,- and connections for causing the current output of said second current transformer to flow "through said, .866 valued reactor and said .5 valued resistor in opposite relative directions.

5. In a line drop compensator, a potential cir cuit, a pair of resistors and a pair of reactors serially connected therein. the relative values of said resistors being in the ratio of .866:.5, the relative valuesof said reactors being in the ratio of .866:.5, a current circuit, first and secondcurrent transformers connected therein, connections for causing the current output of the first current 80 .866 valued resistor and said .5 valued reactor in opposite relative directions, and connections for causing the current output of said second current trans former to fiow through said .866 valued reactor and said .5 valued resistor in the same relative directions.

6. In a line drop compensator, a potential circuit, a pair of resistors and a pair of reactors serially connected therein, one resistor having a value of half the other and one reactor having a value of half the other, the greater valued resistor and reactor being provided with a .866 valued tap, a current circuit, first and second current transformers connectedtherein, means for varying the ratios of said current transformers so as to adjust the resistance and reactance settings of said compensator, and switching means for connecting said current transformers to said resistors and reactors, said switching means having a first position in which the first current transformer is connected to the full valued resistor and the second current transformer is connected to the full valued reactor, said switching means having a second position in which said first current transformer is connected to said half valued reactor and the .866 valued resistor tap and said second current transformer is connected to said half valued resistor and the .866 valued reactor tap.

7. In a line drop compensator, a potential circuit, a resistor and an equal valued reactor connected therein, said resistor having two pairs of terminals between which the resistance values are in the ratio of 11.577, -said reactor having two pairs of terminals between which the reactance values are in the ratio of l .577, a current circuit, first and second current transformers having their primary windings connected therein, means for connecting the first current transformer to the unity valued terminals of saidresistor in series with the .577 valued terminals of the reactor, and means for connecting the second current transformer to the unity valued terminals of said reactor in series with the .577 valued terminals of said resistor.

- each transformer for adjusting the resistance and 8. In a line drop compensator, a potential circuit, a resistor and an equal valued reactor connected therein, said resistor having two pairs of terminals between which the resistance values are in the ratio of l .577, said reactor having two pairs of terminals between which the reactance values are in the ratio of 1:577, a current circuit, first and second current transformers having their primary windings connected therein, means for varying the number of active primary turns of reactance settings of said compensator, the secondary windings of each current transformer having two pairs of terminals between which the output currents are in the ratio of 1:.866, and switching means for connecting the secondary windings of said current transformers to said resistor and reactor, said switching means having a first position in which the unity valued terminals of the first current transformer are connecte to the unity valued terminals, of said resistgr and the unity valued terminals of said secon current transformer are connected to the unity valued terminals of said reactor, said 3 switching means having a second position in which the .866 current valued terminals of the first current transformer are connected to the unity valued terminals of the resistor in series with the .577 terminals of the reactor and the .866 valued current terminals of the second current transformer are connected to the unity valued terminals of said reactor in series with the .577 valued terminals of said resistor.

9. In a line drop compensator, a potential circuit, resistance and reactance connected therein, a single phase current circuit, a pair of current transformers having their primary windings serially connected therein in such a manner that they always carry the same current, means for causing the secondary current of one current transformer to fiow through a portion of said resistance and a portion of said reactance for producing a twocomponent resistance compensation voltage drop.

and means for causing the secondary current of the other current transformer to flow reactance for producing a two-component reactance compensation voltage drop. I

a 20 portion of said resistance and a of said 

